The present invention relates generally to image processing systems and, more particularly, to methods and systems for sampling an image sensor.
Many different types of image capture devices are available for consumer and business use today. Examples of image capture devices include scanners, digital still cameras, digital video cameras and hybrid devices. All of these devices include image sensors which capture pixel data associated with images to be processed. Today, most image sensors are created using one of three different technologies: self-scanned diode technology, charge injection device (CID) technology and charge-coupled device (CCD) technology. Each of these three technologies employ a semiconductor fabrication process that has inherent limitations with respect to the ability to integrate the image sensors with other circuits on the same chip. However, more recently, it has become possible to use CMOS processes to produce image sensors which allows for a higher level of integration between e.g., image sensors and other digital circuitry.
Referring to FIG. 1, one challenge confronted by designers of image sensors, as well as designers of devices and systems which employ image sensors, is to provide a data transfer mechanism 10 (e.g., a data bus) which transfers the image data from the image sensor 12 to another device, e.g., an image processor 14, sufficiently quickly to satisfy a particular application's need for raw image data. For high speed image applications, e.g., high frame rate video recording applications, bandwidth limitations associated with the data transfer mechanism 10 require the image sensor 12 to be sampled for each captured image frame, i.e., the image sensor 10 does not transfer data associated with each and every available image sensor pixel for each captured image frame. For example, the image sensor 12 can be sampled at VGA resolution (640×480) and the resulting sampled data can be transferred over the data transfer mechanism 10 at a rate which is less than or equal to the bandwidth limitations associated with that device. Conventional image sampling techniques do not vary from frame to frame, e.g., sampling the image sensor uniformly from frame to frame to reduce the sample size to VGA resolution. However, CMOS image sensors (as well as potentially other types of sensors) have the capability to be randomly accessed, therefore allowing variable sampling from frame to frame.
Accordingly, it would be desirable to provide techniques and devices which intelligently sample image sensor arrays in a manner which may vary from frame to frame to produce high quality renditions of the images in an output medium.